Following the September 11 attacks in the US, the home secretary, David Blunkett, asked the public to believe that a compulsory national identity card could be a useful tool in the war on terrorism.

His claims were greeted with a mixture of ridicule and disbelief. Security experts, campaigning groups and politicians of all parties raised major concerns about the effectiveness of such a system and the serious impact on civil liberties.

Wisely, the government retreated. But less than a year later, the question of ID cards raises its ugly head again. In the nine months since Mr Blunkett first touted the possibility of introducing cards, the government has suggested a wide range of supposed benefits in order to suit the prevailing news agenda.

Having accepted that ID cards would do nothing to eliminate Osama bin Laden's al-Qaida network, it was then suggested that they had a crucial role to play in tackling benefit fraud. More recently, we have been asked to believe that so-called "entitlement" cards are the solution to preventing illegal immigration.

The government insists that it is "neutral" on the question of ID cards and its public consultation, which begins later this week, is merely intended to generate an honest and open debate. It is hard to take these claims at face value.

There can be little doubt that the government is seduced by the idea of "entitlement" cards as spin doctors now wish to call them. So worried are they about the possible scale of parliamentary opposition, adverse media coverage and a public backlash, that the term "ID card" has been removed from the New Labour lexicon.

A card that "entitles" citizens to a wide range of public services may sound more palatable - but it is simply an ID card by any other name. The purpose of the card would be to establish your credentials, to prove you are who you say you are - in other words to determine your identity.

The home secretary would do himself much credit by openly admitting this, an "honest and open" public debate can only proceed if he is honest about the nature of the card he is proposing.

The practical concerns about introducing a nationwide card scheme are manifold. A set-up cost of more than £1bn and running costs of hundreds of millions of pounds a year would need to be properly justified. The Home Office's record at implementing such new technological programmes leaves much to be desired. And while it claims that it would not be a legal requirement to carry the card at all times, card ownership would still be compulsory.

One can only imagine how the authorities will attempt to enforce a 100% sign up to the new scheme, even a relatively small number of people failing (or refusing) to register for the card could render the whole system unworkable.

But while practical and financial problems loom large, the possible threat to individual liberty and our rights to privacy are even greater.

The continual refrain from the cards' supporters - "you have nothing to fear if you have nothing to hide" - cannot go unchallenged.

Only recently, a special adviser to the Department of Transport was forced to apologise for using his time to investigate the political affiliations of survivors of the Paddington rail disaster with, one presumes, the intention of rubbishing them in the media.

While the government would have us believe that this was an isolated incident, it surely raises very serious questions about exactly what information we are willing to place in the hands of the state bureaucracy and who has access to it.

Any form of ID card scheme would require a national database storing vast amounts of sensitive information on every one of us. You would have to be supremely uncynical or incredibly naïve to believe that the database will only be deployed in catching the guilty.

Mr Blunkett also recently proposed a "snoopers' charter", enabling a myriad of public authorities to access information about the public's telephone calls and emails. Although he was forced to back down in the face of substantial public opposition, there can be no doubt that the instincts of this government are to allow greater and greater state access to more and more information about every British citizen. A national identity card would accelerate this trend.

The threat of terrorism, the scale of social security fraud and our approach to asylum seekers are all serious problems in today's Britain. But an identity card scheme provides no more than the illusion of a solution to these or a whole range of other social issues. We are going to have to focus our efforts and our policies in cleverer and more sophisticated ways. A policy of casting the net so wide that all 60 million British citizens are entangled in it makes it much easier for the small number of terrorist operatives, serious fraudsters and other criminals to slip through the system.

Following the extensive public debate that the government is promising, one can only hope that common sense will prevail and that plans for an ID card scheme will be put back on the Home Office shelf or, better still, consigned to the dustbin.